1. Field of the Invention
The present invention is directed to the field of apparatus for mixing the components of a multiple component sprayable fluid. More particularly, the present invention is directed to that portion of the above-noted field which is concerned with the mixing of a multiple component sprayable fluid wherein coreaction of the fluid components such as, for example, crosslinking will begin to occur immediately upon mixing. More particularly still, the present invention is directed to that portion of the above noted field which is concerned with the provision of sprayable fluids having a high percentage of solid material for use as coatings and wherein a color-providing component and a crosslinking component which may be color-free may be intermixed to provide for a coating having a selected color property and wherein crosslinking between the crosslinking component and the color-providing component will begin to occur immediately upon introduction of the color-providing component into the clear crosslinking component. More particularly still, the present invention is directed to that portion of the above-noted field which is concerned with the provision of apparatus for mixing the color-providing component and the crosslinking component of a multiple component color coating which will maintain a minimum quantity of intermixed components during use.
2. Description of the Prior Art
The recently experienced "energy crisis" has prompted extensive investigation by industry into the potentials for reducing energy consumption without materially or adversely affecting the quality or quantity of the goods and services provided. Substantial quantities of energy are consummed in the coatings applying industries in the operation of the ovens in which sprayed coatings are crosslinked.
Recently developed multiple component sprayable coatings appear to offer a potential for reducing oven temperatures, and hence energy consumption, without adverse affect to the quality of the finish or the time required for complete crosslinking of the coating. Examples of multiple component coatings are available under the names Polane from Sherwin-Williams Company, Inron From E. I. DuPont de Nemours and Company, and Akrylthane from Cook Paint and Varnish Company. These coating materials normally include a crosslinking "accelerator" which is capable of increasing the rate of crosslinking at any given temperature. A common accelerator is di-butyl 10 di-laurate, although others are known. By varying the quantity of accelerator present in a coating, the crosslinking rate may be varied. The presence of any of the accelerator induces a tendancy to crosslink at low, ambient, temperature necessitates the maintaining of the material in component form until immediately prior to application as a coating. However a practical upper limit of accelerator content has heretofore prevented any substantial reduction in oven energy expenditures.
As the crosslinking rate at ambient temperatures increases, the quantities of mixed presprayed, and hence crosslinking material also increases. Thus, it has been necessary to keep the quantity of mixed and presprayed multiple component material to a minimum. In those instances where the components are premixed, the quantity of premixed material has necessarily been very limited, for example, in quart quantities. It is therefore an object of the present invention to provide an improved spray apparatus to facilitate the use of sprayable coating materials having high crosslinking accelerator content in high volume mass-production coatings operations.
A further problem has been encountered with the use of such materials in coating operations requiring frequent color changes. In order to change color, substantial quantities of solvent must be expending in order to remove all vestiges of coating material, particularly crosslinked, from the spray apparatus. The greater the quantity of crosslinked material, the greater the quantity of solvent required. This is wasteful, both of solvent and of coating materials which tend to be very expensive in multiple component coatings. The large amounts of solvent used also greatly increases the amount of stationary source emissions contributing to atmospheric pollution. It is therefore a further and specific object of the present invention to provide such an improved spray apparatus which will maintain only very small quantities of presprayed multiple component coating materials in a mixed, and hence crosslinkable, condition.
Air atomizing spray guns are well known in the sprayable coatings field. Large numbers of such guns are in existence and in daily use. It is therefore a further object of the present invention to provide apparatus, or association with a conventional air atomizing spray gun, which will continuously and intimately intermix the components of a multiple component spray coating and which will result in only very small minimum quantities of mixed and yet to be sprayed fluid being present at any one time. More particularly, it is an object of the present invention to provide convenient apparatus for attachment to a conventional air atomizing spray gun which may receive separate fluid flows of the components of a multiple component sprayable coating and which will continuously mix these components and deliver them in a mixed state to the spray nozzle of the air atomizing spray gun. It is a further object of the present invention to provide such apparatus with means for easily cleaning the apparatus of mixed coating material to accomplish a change in the material being sprayed. It is a further object of the present invention to provide apparatus for addition, or attachment, to a conventional air atomizing spray gun which will not significantly increase the bulk or mass of the air atomizing spray gun so as to avoid any significant alteration in the work requirements for such gun when applied to a manual spray operation.